using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEditor;
using UnityEditor.Experimental;
using UnityEditor.ProjectWindowCallback;

// Add "New Prefab" asset creation menu items.
public static class CreatePrefabAssetEditorMenu
{
    class DoCreatePrefabAsset : EndNameEditAction
    {
        // Subclass and override this method to create specialised prefab asset creation functions
        protected virtual GameObject CreateGameObject(string name)
        {
            return new GameObject(name);
        }

        public override void Action(int instanceId, string pathName, string resourceFile)
        {
            GameObject go = CreateGameObject(Path.GetFileNameWithoutExtension(pathName));
            GameObject prefab = PrefabUtility.SaveAsPrefabAsset(go, pathName);
            GameObject.DestroyImmediate(go);
        }
    }

    class DoCreateUIPrefabAsset : DoCreatePrefabAsset
    {
        protected override GameObject CreateGameObject(string name)
        {
            var obj = new GameObject(name, typeof(RectTransform));
            obj.layer = LayerMask.NameToLayer("UI");

            // Add a child with CanvasRenderer so that the prefab editor knows to use the UI stage.
            var canvas = new GameObject("Image", typeof(CanvasRenderer), typeof(UnityEngine.UI.Image));
            canvas.transform.SetParent(obj.transform, worldPositionStays: false);
            return obj;
        }
    }

    static void CreatePrefabAsset(string name, DoCreatePrefabAsset createAction)
    {
        string directory = GetSelectedAssetDirectory();
        string path = Path.Combine(directory, $"{name}.prefab");
        ProjectWindowUtil.StartNameEditingIfProjectWindowExists(0, createAction, path, EditorGUIUtility.FindTexture("Prefab Icon"), null);
    }

    static string GetSelectedAssetDirectory()
    {
        string path = AssetDatabase.GetAssetPath(Selection.activeObject);
        if (Directory.Exists(path))
            return path;
        else
            return Path.GetDirectoryName(path);
    }

    [MenuItem("Assets/Create/Prefab", isValidateFunction: false, priority: -20)]
    public static void CreatePrefab()
    {
        CreatePrefabAsset("New Prefab", ScriptableObject.CreateInstance<DoCreatePrefabAsset>());
    }

    [MenuItem("Assets/Create/Widget", isValidateFunction: false, priority: -20)]
    public static void CreateWidget()
    {
        CreatePrefabAsset("New Widget", ScriptableObject.CreateInstance<DoCreateUIPrefabAsset>());
    }
}